1. Field of the Invention
The present invention relates to an insecticidal mat containing an insecticidal ingredient, and to a heat-transpiration insecticidal method in which the mat is set on a radiation plate of a portable heat-transpiration apparatus to thereby transpire the insecticidal ingredient.
2. Description of the Related Art
Hitherto, as a method of heat-transpiring an insecticidal ingredient for killing insects or the like, (1) a mosquito-repellent incense, (2) an electric mosquito-repellent mat have been used favorably, and (3) a liquid mosquito-repellent, that is, a method of heat-transpiring an insecticidal solution by soaking an absorbent wick in the insecticidal solution and heating the upper part of the wick has been popular in recent years.
Of those, the electric mosquito-repellent mat works by means of setting a fibrous mat impregnated with an insecticidal ingredient on a radiation plate of the heat-transpiration apparatus, and heating the mat with electricity to transpire the insecticidal ingredient contained therein. The temperature at the central portion of the radiation plate is generally set in the range of 140 to 180xc2x0 C. The mat which is effective for 8 to 10 hours in a room of about 10 m2 contains, for example, about 40 mg of allethrin as the insecticidal ingredient per mat. However, such an electric mosquito-repellent mat is for use in a closed room, and of course cannot be used outdoors where there is no power supply. For this reason, development of a portable mosquito-repellent utilizing a battery, or oxidation heat or burning heat of liquefied gas is progressing. For example, Japanese Patent Examined Publication No. Hei. 5-81801 discloses a portable heat-transpiration apparatus comprising a burner means which flame burns a fuel in a pipe to heat the pipe as a heating member, and a disposable and exchangeable fuel cartridge which supplies a fuel to this burner means, wherein the fuel cartridge has a fuel supply valve means which controls flow of fuel. Recently, mosquito-repellent sets utilizing this portable heat-transpiration apparatus are commercially available. However, its use time is short as about 4 hours, and improvement is demanded in the point of sustainability of the insecticidal effect, or the like.
An object of the present invention is to provide an insecticidal mat which is applied to a portable heat-transpiration apparatus and is capable of continuously maintaining an insecticidal effect over 8 hours or longer even in an open space such as the outdoors, and a heat-transpiration insecticidal method using the same.
In order to attain the object described above, the present inventors investigated in detail the shape of a fibrous mat, the kind and composition of an insecticidal ingredient impregnated in the fibrous mat, and a combination with performance of a portable heat-transpiration apparatus, to thereby find that the insecticidal effect can continuously be maintained over 8 hours or longer even in an open system space such as the outdoors.
That is, a first aspect of the present invention relates to an insecticidal mat comprising a fibrous mat having a size of 1,000 to 2,500 mm2 which contains 250 to 600 mg of allethrin as an insecticidal ingredient, 600 to 1,000 mg of piperonyl butoxide as a volatization controlling agent and 10 to 100 mg of at least one member selected from the group consisting of 2,5-di-t-butylhydroquinone, 3,5-di-t-butyl-4-hydroxytoluene and 3-t-butyl-4-hydroxyanisole as a volatization controlling agent per mat, wherein the mat is used by setting on a radiation plate which has an area of 1,000 to 2,500 mm2, has a temperature of 150 to 190xc2x0 C. at its central portion, and has a temperature difference of 10xc2x0 C. or less between the central portion and its edge portion.
In the present invention, the fibrous mat having a size of 1,000 to 2,500 mm2 is used in order to increase a transpiration amount of the insecticidal ingredient per unit time, thereby exhibiting a sufficient insecticidal effect even in an open space.
As the material of the fibrous mat, that of the same quality as the conventional mosquito-repellent mats such as pulp, linter, or a mixture of them can be used. The mat having a thickness of 1.5 to 3.0 mm can be used with ease.
The insecticidal ingredient used in the present invention is allethrin of a pyrethroid compound having high safety. The allethrin has a vapor pressure at 20xc2x0 C. of 5.6 mPa and is suitable as an insecticidal ingredient for a heat-transpiration apparatus used in an open space. Optical isomers based on asymmetric carbon in a chemical structure, such as each or any mixtures of pynamin forte, bioallethrin, esbiothrin and esbiol, can of course be included in the insecticidal ingredient of the present invention.
The allethrin is contained in an amount of 250 to 600 mg per mat. If the amount is less than 250 mg, the insecticidal effect cannot be exhibited over a long period of time. On the other hand, if the amount exceeds 600 mg, there is caused difficulty in the impregnation in the insecticidal mat, which is not preferable.
The insecticidal mat of the present invention contains a volatilization controlling agent in order to sustain the insecticidal effect in an open space. The volatilization controlling agent is used in a combination of 600 to 1,000 mg of piperonyl butoxide which is suitable for allethrin and 10 to 100 mg of at least one member selected from the group consisting of 2,5-di-t-butylhydroquinone (compound A), 3,5-di-t-butyl-4-hydroxytoluene (compound B) and 3-t-butyl-4-hydroxyanisole (compound C). That is, compounds other than piperonyl butoxide known as a volatilization controlling agent, such as butyl stearate or octachlorodipropyl ether, are not suitable for use in the present invention, and satisfactory volatilization controlling effect cannot be obtained by the use of piperonyl butoxide alone. The present invention is characterized in the combination of at least one member selected from the group consisting of compound A, compound B and compound C with piperonyl butoxide.
If the amount of piperonyl butoxide contained is less than 600 mg, the volatilization controlling effect becomes poor, and on the other hand, if the amount exceeds 1,000 mg, the insecticidal effect is suppressed, and also there is caused difficulty in the impregnation in an insecticidal mat, which are not preferable.
At least one member selected from the group consisting of compound A, compound B and compound C is contained in an amount of 10 to 100 mg, preferably 30 to 60 mg, per mat, thereby exhibiting the volatilization effect in combination. If the amount is less than 10 mg, the volatilization controlling effect is not obtained, and on the other hand, if the amount exceeds 100 mg, the insecticidal effect is suppressed. Further, because those compounds are crystalline, there is the problem that if the amount thereof exceeds 100 mg, it is difficult to dissolve. Of the above three kinds of compounds, 2,5-di-t-butylhydroquinone (compound A) is most preferable, and combination of this compound with piperonyl butoxide exhibits particularly excellent volatilization performance, thereby sustaining the insecticidal effect over a long period of time.
In preparing the insecticidal mat of the present invention, an undiluted solution (base solution) is used which is generally obtained by adding perfumes, dyestuffs and the like, and also solvents such as kerosene, to the above described allethrin and volatilization controlling agent. However, there is set a limit on the maximum holding liquid amount in the mat. Therefore, the amount of undiluted solution is preferably used in an amount of 1.5 g or less per mat in the case of the mat having a size of 35xc3x9750 mm and a thickness of 2.0 mm.
In the present invention, insecticidal ingredients other than allethrin, for example, furamethrin, prallethrin, empenthrin, transfluthrin, acaricides, repellents, spatial bactericides and antibacterials such as hinokitiol, linalool, citral, pinene, menthol, terpene alcohols, etc., and fungicides and the like can be added to give a multipurpose composition so long as the transpiration property of the allethrin is not impaired.
The portable heat-transpiration apparatus used in the present invention is used in an open space such as outdoors, and therefore requires efficient and high heat energy as compared with use in indoors. For this reason, the radiation plate is required to have an area of 1,000 to 2,500 mm2, a temperature at the central portion of 150 to 190xc2x0 C., and temperature difference between the central portion and edge portion thereof of 10xc2x0 C. or smaller. The apparatus described in Japanese Patent Examined Publication No. Hei 5-81801 is suitable as the portable heat-transpiration apparatus capable of maintaining this heating temperature stable. That is, the apparatus is a type comprising a burner means which flame burns a fuel in a pipe to heat the pipe as a heating member, and a disposable and exchangeable fuel cartridge which supplies a fuel to this burner means, wherein the fuel cartridge has a fuel supply valve means which controls flow of fuel. The fuel is generally butane gas. When, for example, a fuel cartridge containing 12 g of butane gas is mounted to this heat-transpiration apparatus, it is possible to continuously use for about 10 hours.
The portable heat-transpiration apparatus used in the present invention is appropriately equipped with switch, safety protection cover, heat generation indicator and the like in addition to the heating means, heat radiation plate, fuel supply means and the like. However, its specification is not particularly limited, and may be determined according to the conventional heat-transpiration apparatus.
A second aspect of the present invention is the structure according to the first aspect, wherein the portable heat-transpiration apparatus is the above-described fuel cartridge of flame burning type.
A third aspect of the present invention relates to a heat-transpiration insecticidal method, comprising impregnating a fibrous mat having a size of 1,000 to 2,500 mm2 with 250 to 600 mg of allethrin as an insecticidal ingredient, 600 to 1,000 mg of piperonyl butoxide as a volatilization controlling agent, and 10 to 100 mg of at least one member selected from the group consisting of 2,5-di-t-butylhydroquinone, 3,5-di-t-butyl-4-hydroxytoluene and 3-t-butyl-4-hydroxyanisole as a volatization controlling agent per mat, setting the mat on a radiation plate of a portable heat-transpiration apparatus, which has an area of 1,000 to 2,500 mm2, has a temperature of 150 to 190xc2x0 C. at its central portion, and has a temperature difference between the central portion and its edge portion of 10xc2x0 C. or less, and maintaining the insecticidal effect continuously over 8 hours or more in an open space.
A fourth aspect of the present invention is the method according to the third aspect, wherein the portable heat-transpiration apparatus is the above-described fuel cartridge of flame burning type.
The combination of the insecticidal mat and the portable heat-transpiration apparatus, having the structures described above is particularly useful in the case of using in an open space such as camp, fishing, barbecue, garden work or the like. High insecticidal effect is maintained to sanitary noxious insects such as mosquito or fly, nuisance insects such as blackfly (gnat), a chironomid, a casemaking clothes moth, a webbing clothes moth, a carpet beetle and the like over 8 hours or more. In addition, safety, usability and the like are excellent.